1. Field of the Invention
The present invention relates to a sanitary fitting.
2. Discussion of the Background
There are conventional sanitary fittings in which the quality of the feed water can be endangered on re-suction of impure water into the feed line. These include, in particular, wash basin and sink fittings having a pull-out hose shower and shower and bath tap units having a hose shower. It can occur in the case of fittings of this type that the shower is lying in a basin or in a bath when, for example, the feed line breaks. If the fitting is open at that moment, the water in the basin or the bath can be completely sucked out via the shower due to the negative pressure which is built up in the feed line due to the water flowing off. Impure water can thus pass into the feed line and emerge again later after repair at the corresponding fitting or even at a different location. For this reason, fittings of this type must have safeguards, by means of which re-suction of impure water into the feed line is prevented.
Sanitary fittings having pull-out hose showers, for example produced by KWC AG, Unterkulm, Switzerland, are freely available on the market, which fittings have a nonreturn valve which is installed in the shower itself in order to prevent a backflow of impure water into the feed line. However, nonreturn valves of this type are not considered by all authorities to be sufficiently reliable since spring fractures or other types of malfunctions have to be expected. DIN 1988, part 4, dated Dec. 1988 lists safeguards which prevent undesired backflow of impure water into the feed line. Furthermore, DIN 3266, part 1, dated July 1986, describes in detail safeguards of this type, such as, for example pipe interrupters or pipe aerators. These safeguards have an aeration aperture which is closed in the case of normal outflow of water from the fitting, but is open at least under conditions permitting backflow of water in order to ventilate the outlet line for the water between the safeguard and the outlet. At the same time, the feed line is separated in terms of flow from the outlet line. It is possible under certain conditions that small amounts of leakage water may escape from the aeration aperture. This is the case, for example, if there is positive pressure in the hose portion of the hose shower when the aeration aperture of the safeguard is exposed in order to prevent backflow of impure water into the feed line. Although these quantities of leakage water are usually small, they can lead to undesirable damage and impurities. However, it should also be noted that greater quantities of water may escape from the ventilation aperture as a result of a defect.
A sink tap unit is known from DE-U-G 88 13 390.7. The one-piece fitting housing has a nozzle projecting toward the front, through which a hose portion of a hose shower is guided and into which the shower can be inserted. A safeguard for preventing the backflow of water into the feed line is installed in the control cartridge constructed as a piston mixer. The control cartridge has an aeration aperture which is closed under normal operating conditions by a rubber disk. If, in contrast, a negative pressure is built up in the feed line, the rubber washer exposes the aeration aperture in order to ventilate the feed line. The aeration aperture is connected to the surroundings by an aeration channel which is arranged in the nozzle and opens out into the interior of the nozzle in the vicinity of the free end of the nozzle. In the case of water leakage passing through the aeration aperture into the aeration channel, said water leakage runs through the interior of the nozzle and the fitting housing in an uncontrolled manner which can lead to undesirable impurities and damage. Furthermore, the hose is subjected to undesirable severe bending loads as it emerges from the nozzle if it is pulled sideways.